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Development Team Member
Posts: 2
This is my first post on the forum so I should introduce myself. I have coached cross country skiing for over 40 years including 13 years with the Canadian National team. I have raced off and on through this period both in xc skiing and cycling.

 I have been through just about every kind of test and apparatus for testing during this time. From Douglas air bags to YSR lactate analyzers to all of the newer portable, digital analysis tools.

For over 40 years we have worn heart rate monitors. For much of that time we poked fingers to collect lactate but since Juerg and others have refuted lactate and lactic acid we have stopped. (not everyone has stopped, by the way. I was just down watching testing done at the Canadian Sport Institute of Ontario on the Ontario ski team and they were collecting lactate to set training zones). I have 2 power meters and use them every time I ride my bike.

When I first heard and read about MOXY monitors I was very excited that maybe we would finally have something that would help to make coaching easier and answer many of the questions that we coaches have about training properly and efficiently. 

In xc skiing, as in most other endurance sports we tend to do a little or a lot of every kind of training, not really knowing what is working or not but afraid to miss anything so we do everything. I thought that the MOXY monitor would help me to eliminate or reduce a lot of unnecessary work by me and my athletes.

I did try the BSX Insight first but was unhappy with the technology and also unhappy that it would only test on the calf muscle. XC skiing is a total body exercise so just testing on the calf is very limiting.

However, so far I have collected a whole lot of data but this data is so variable and so far from what is written on the MOXYmonitor website that I find that instead of getting answers I have more questions and I am no closer to what I want which is to be able to create training zones and find limiters and help my athletes to go faster.

As I see it the steps in using technology like this are:
1. collect data
2. interpret the data 
3. compare the data to existing data
4. use the data to move forward

My biggest complaint in working with exercise physiologists is that they can test athletes to find out what has happened from what they have done but they cannot help with step 4. And, if the data is as variable and as far from what is supposed to be the norm like the data that I have collected on myself then it is impossible to go forward to step 4. 

As a coach and athlete I AM interested in a "cookbook" as Juerg would put it. What I mean is that I would like to have something that would tell me that if I see this then I should do this, or this, or this. I cannot find that anywhere out there about the MOXY. Just a whole lot of data and people guessing what it means. 

So, having said that I would like to post here a file with a step test that I did today. I started out doing the standard 5 minute step test with the MOXY on my right VL using the protocol that is written in the cycling guide on the MOXY website. I controlled the intensity with wattage on my bike and had my Tacx trainer set at 0 degrees of slope.

As you can see the % of O2 saturation starts very low and instead of rising in the first steps it drops with each step. This is not the first time that I have done this test and it repeats 2 other tests that I have done. 

My first questions is - why is the O2 saturation so low on this muscle? Is this the reason why it does not go up during the very easy stages at the start?
So, after resting 5 minutes I decided to repeat the test, this time with the slope of the trainer set at 3% to simulate going uphill. The O2 saturation and tHb seem to be close to the same levels (maybe a little higher because of the rebound from the 1st test) but consistent. Still very low compared to tests that I have seen from others and tests that are used as examples on the MOXY website and in their literature. 

So I decided to do the step test one more time, this time moving the MOXY a couple of inches over so that now it is on the Rectus femoris. Look at the difference - much higher O2 saturation and much lower tHB and much different results. A little bit more of a plateau but again, not the perfect graph that I could use to create the training zones that I would like to use. This is consistent with what has happened in other workouts. If I move the MOXY on the RF up or down the width of the MOXY I can get readings that are 10-20% different. Why and what is the best place to put the monitor on every muscle to get accurate and repeatable readings.

I am not a scientist or a data geek. I am a coach and athlete who spent a lot of money to try to improve performance, not to have some nice numbers to look at and discuss. Practical advice would be very helpful. Thanks

Attached Files
csv 5 minute step test x 3.csv (287.54 KB, 22 views)


Development Team Member
Posts: 5
I will start from end [smile]

moxy forum is mainly theoretical [biggrin]

placement of device - imho biggest "trouble" for easy interpretation. There shoud be anything under device...   


Development Team Member
Posts: 159
Hi Jackxc. Welcome to the forum. Different people have different muscle coordination patterns. In cycling I am very VL dominant. You might be more RF dominant which would give better reading if the moxy is placed on the RF. The readings can vary if you change the placement on the muscle. On your VL try moving it a couple of cm higher up the leg and see if you get readings that make more sense. The main thing are the trends you see, not the absolute values.

Fortiori Design LLC
Posts: 65


First, it is important to understand some rules and limitations of NIRS and Moxy in regard to the data you are collecting. When we are comparing a measured value, like your difference in RF and VL we need to be careful as the margin of error is larger here and we could make an alpha error. Within 10% differences we do not consider a difference. So in the case of RF and VL, or right and left, if the numbers are within 10% (51% and 60% for example), this is looked at as the same. Once the range is bigger than 10% now we have increasing confidence that there is actually some physiology to differentiate, and would start to look at some different data to see if we get some additional information. For example in a left right comparison, are the left and right both producing the same power? That being said, about the value, comparing trends are much more robust. Which means if you have one measurement down trending by 5%, and another by 9%, this is much more accurate to compare, as a great down trend in B than in A. What you can see in your example, is that generally all three test have very similar trends (two are the same so they should). If you take a look at the Andrew Coggan webinar he shows some data that identifies same trending across a wide range of lower body muscles when cycling.  I hope that is a first step.

This goes directly into the question of SmO2% and low values, can that be? Well its hard to get a solid answer as muscle capillary measurements in vivo and in situ is rather difficult. However, generally values under 20% are excepted, especially looking at SmO2 rather than StO2. If a 0% values is really 0%? Likely not, gain we consider the 10% range. But a 0%, or 3% or 5%, just means very very low. It means you have essentially reached a maximally deoxygenated state where you are extracted and utilizing all the supplied O2. In many ways with NIRS we talk much more about maximally deoxygenated states, rather than an absolute % of SmO2 as this is difficult to prove.

For tHb, we do not compare the values at all, only the trending.

Having hopefully clarified these points, I look forward to your questions, closer to type 4 you mention. Ill give a quick insight that may help. If you look at tHb in your 3rd RF test and compare that to your 1st and 2nd VL test you can see that the tHb trending is a little different. You can see that in the RF test tHb is a little more dynamic and moves a little with SMO2 and at the end increases. tHb is an indirect measure of blood volume changes. This means that you have a more dynamic blood volume change in the RF than in the VL. This of course could then account for higher SmO2 values and slightly different trends. 


Development Team Member
Posts: 349
Hi JackXC

Welcome to the forum, thanks for sharing the data.

A couple of perspectives - these are not meant to be antagonising, please interpret them in the spirit that they intended (which is just to try provide you with an honest perspective, personal experience of the forum).
- You are not alone. Many have expressed similar frustrations with similar sentiments.

- The culture of the forum that Juerg has created is very much one of think for oneself, rather than have answers and solutions presented . Personally this is what I and many others love about it, even though it can be super frustrating when something is ambiguous or I don't yet understand it sufficiently. It requires much more patience, but the reward is much greater. I understand that this is not for everyone. Its also clearly established from Juerg's side that the idea is not to discuss training ideas (i.e. your point 4). That is not to say they don't exist, just generally that they don't get very far on the forum. Really the point though is that if you are looking for a training decision tree about if this then do that, if this then do that then i think you will be disappointed with what you can get out of the forum. 

- You mention that you say that you would like a "cookbook". I would like to challenge this point in that if such a cookbook is able to exist, what value does a coach add to the process? If the athlete can just follow the training program decision tree themselves a coach is potentially just reduced to a training project manager and/or cheerleader for the athlete, or for athletes who have the discipline and motivation themselves the coach is not required at all. If i was a coach the very last thing i would want is a cookbook, because it creates a commodity out of the part of the value chain that i operate in. Personally i would welcome tools that have the potential to add immense value, but require complex synthesis and experience that range across performance , physiological etc, that I can leverage that others cannot. 

- You mention two interesting points. (1) That you have performed the tests with consistent results on yourself and (2) that your results look different to "textbook" profiles. Now point (1), to an extent, tells you effectively that you are using a reliable feedback tool - i.e. it is not some anomalous assessment. Point (2) tells you that the physiological response is totally unique to you as an individual. A window into the unique physiology of an athlete is surely something to get super excited about for a coach, rather than trying to force fit it into an existing paradigm of each athlete mapping neatly into generic "training zones". You seem to be frustrated that you don't fit the "textbook" when in fact highlighting how you don't fit the textbook is surely the very unique value that such a tool can bring?

- If you can consider re-aligning your expectations slightly and engage in the forum with (1) patience and (2) focusing on step number 2 in your list, i have no doubt that with your 40 years of coaching experience at the top level, access to assessing a wide range of athletes etc, step 4 will start to happen automatically and you will start to generate insights and thoughts many of us, could only dream about coming up with. Perhaps a place to start is just to use Moxy as a feedback tool with your existing methods - see differences in athletes, see how the results are different to what you would have expected and slowly it might become clearer why some athletes are responding well to some training interventions while others are not.

- Undoubtedly there are examples of practical application leading to forward performance progress through using Moxy as a tool. As an example follow some of the stuff that Sebo2000 has posted on the forum. 

Then some thoughts on your specific assessment:
  1. Is there a reason that you are not doing a 5-1-5 assessment protocol rather than step-test?
  2. Keep in mind the assessment is sport-specific
  3. If you think of 02 saturation as being reflective of the tension between oxygen delivery and utilisation then: In the "textbook" case of Sm02 increasing initially and then decreasing, think of what would most likely be going on with delivery and utilisation at each intensity - and why you see that Sm02 trend. Now in your case you see something different so what could be different from you to the "textbook"? Then you see a different pattern on RF and VL, tying into Craig and Andri's points what does this tell you about the relative demands and supply to these muscles relative to each other at different intensities?
Just at a macro level, imagine an athlete with exactly the opposite profile to you. Their Sm02 increases at low intensities, but  their Sm02 does not reach low levels at all even in the high intensities (say they observe similar profiles on both RF and VL for the sake of the example). That alone would provide direction for how training might differ for the two athletes i.e. as a coach what is the relative mix of training that is going to focus on delivery vs utlisation and how is it different for the two athletes, to move performance forward. This is obviously a gross over-simplification but hopefully provides the principle.

Again, the post is not intended to come across as attacking in any way. It is meant as a constructive discussion on the valid points and frustrations you raised.


Development Team Member
Posts: 2
Hi everyone. Thank you for taking the time to reply. ryinc, I have also done a couple of 5-1-5 tests on my bike trainer and I am attaching the csv file for the first one that I did. I have also done the step test on roller skis with an 8 minute step that was recommended by Juerg and on my bike trainer with an 8 minute step length. I can upload these tests as well if you would like to see them. Again, because they do not "conform" to what is talked about on the MOXY website it is very hard for someone new, like me to make an interpretation of the data.

I feel a little bit like the newcomer to a gym who has paid his membership but has no info on how to use the equipment and stumbles around from machine to machine trying to figure out what to do and then basically stops coming because there is not enough information available to help him to use the equipment correctly. At the moment I have quite a bit of data but cannot interpret it or find out where i can learn how to interpret it so I feel like I am wasting my time.

It is eerily similar to my years trying to interpret lactate data. A lot of conjecture and theories that all eventually turned out to be refuted by many of the same people who were telling me how good it was to test and use lactate. You only have to listen to all of the people who still talk about the lactic acid burn in muscles even now to see how much those theories are still entrenched in the sport community.
My athletes are looking for ways to get better faster. They are not really interested in being "crash test dummies". I see that all the time with the testing that is done on athletes and if you ask most of them they will tell you that they have gotten very little from most of the testing done on them in the past. They are looking for practical ways to help them to make sure that they are training efficiently and properly and for practical tests that will tell them whether or not what they have done in training has helped them to improve their sport. And, of course, the holy grail - if this is where I am now, and this is what I have done then this is what I should be doing to get better.

I was hoping that the MOXY monitor would do a better job of helping me to do that with them but so far, for me, in my endurance sports I have seen nothing that tells me that this is any better than lactate or heart rate or power or RPE for monitoring training or testing. If anyone can put me on to people who have started down the path to answers to these questions I would appreciate your help. Thanks

Attached Files
csv 5-1-5 test based on FTP 240 watts.csv (277.44 KB, 22 views)


Development Team Member
Posts: 191
Hi Jack, welcome to the forum. I will give you my interpretation on your 515 soon [smile]

Development Team Member
Posts: 349
Hi Jack

Had a longer look at the files.

My sense is that muscle oxygen utilisation is pretty much ruled out as a limiter (at least for VL muscle).

Overall it looks like a supply side limitation, but i don't see any very clear evidence of respiratory limitation, so looks more likely to be cardiac as the limiter to me - although this is without seeing any HR data. The HR data and doing a 5-1-5 assessment on a non-priority (e.g. deltoid) muscle might be informative too.

As mentioned earlier on the thread by Craig the possibility of being VL dominant (possibly a co-ordination issues) exists.  For example, in the step test on RF there does seem to be one sudden drop in RF Sm02, presumably where RF is being more significantly called on to try meet the load. In the 5-1-5 after Sm02 having a downward trend generally in the last load it plateaus a little. In fact if you do the calculations, and analysis in a "biased" view and look carefully you can actually see HHb (i.e. deoxygenated hemoglobin) actually decreases during the 3rd from right interval indicating that utilisation reduced slightly on the VL muscle at this point. These perhaps support the idea that the additional load is being picked up elsewhere due to slightly change in technique/co-ordination. 

That looked like a long 5-1-5 assessment! You could probably run wider gaps in intervals to shorten without losing much insight.

Take the above with the appropriate degree of caution - just a hobbyist's interpretation of the data.


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